Charge sharing correction methods for sub-pixellated radiation detector arrays

Abstract

Various aspects include methods of compensating for issues caused by charge sharing between pixels in pixel radiation detectors. Various aspects may include measuring radiation energy spectra with circuitry capable of registering detection events occurring simultaneous or coincident in two or more pixels, adjusting energy measurements of simultaneous-multi-pixel detection events by a charge sharing correction factor, and determining a corrected energy spectrum by adding the adjusted energy measurements of simultaneous-multi-pixel detection events to energy spectra of detection events occurring in single pixels. Adjusting energy measurements of simultaneous-multi-pixel detection events may include multiplying measured energies of simultaneous-multi-pixel detection events by a factor of one plus the charge sharing correction factor.

What is claimed is: 
     
       1. A method for correcting spectra measured by an imaging radiation detector comprised of an array of pixels each of which is comprised of an array of sub-pixel detectors to account for charge sharing effects, comprising:
 measuring radiation energy spectra by the imaging radiation detector using processing circuitry capable of registering simultaneous, coincident detection events occurring in two or more sub-pixel detectors within any pixel; 
 summing energy measurements of detection events occurring simultaneously in two or more sub-pixel detectors within a pixel which comprise sub-pixel simultaneous detection events to obtain a first energy measurement of multi-subpixel detection events; 
 adjusting the first energy measurements of sub-pixel simultaneous detection events by a sub-pixel charge sharing correction factor to account for inter-sub-pixel charge loss effects; and 
 determining a corrected gamma photon energy spectrum by adding the adjusted energy measurements of sub-pixel simultaneous detection events to gamma photon energy measurements of detection events occurring in single sub-pixel detectors which comprise single-sub-pixel detection events. 
 
     
     
       2. The method of  claim 1 , further comprising determining the sub-pixel charge sharing correction factor by:
 exposing the imaging radiation detector to radiation from a source of gamma photons of a known energy or energy spectrum; 
 estimating gamma photon energies for sub-pixel simultaneous detection events by summing energy measurements by the two or more sub-pixel pixel detectors; and 
 determining the sub-pixel charge sharing correction factor based upon the known energy or energy spectrum of gamma photons from the source and the estimated gamma photon energies from sub-pixel simultaneous detection events to account for the inter-sub-pixel charge loss effects. 
 
     
     
       3. The method of  claim 2 , wherein adjusting the energy measurements of sub-pixel simultaneous detection events by a sub-pixel charge sharing correction factor comprises multiplying measured energies of sub-pixel simultaneous detection events by a factor of one plus the sub-pixel charge sharing correction factor. 
     
     
       4. The method of  claim 2 , wherein determining the sub-pixel charge sharing correction factor is performed for each pixel detector individually to determine a sub-pixel charge sharing correction factor for each pixel. 
     
     
       5. The method of  claim 4 , wherein determining the corrected gamma photon energy spectrum is performed for each pixel by:
 summing energy measurements of sub-pixel simultaneous detection events within each pixel detector to obtain a first energy measurement of multi-subpixel detection events in each pixel; 
 adjusting the first energy measurements of sub-pixel simultaneous detection events in each pixel detector by the sub-pixel charge sharing correction factor determined for each pixel detector; and 
 determining a corrected gamma photon energy spectrum for each pixel detector by adding the adjusted energy measurements of sub-pixel simultaneous detection events to energy measurements of single-sub-pixel detection events in each pixel detector. 
 
     
     
       6. The method of  claim 1 , further comprising determining the sub-pixel charge sharing correction factor by:
 exposing the imaging radiation detector to radiation from a source of gamma photons of a known energy or energy spectrum; 
 determining a first energy spectra for detection events occurring in single sub-pixel detectors and determining its peak value V SPpeak1 ; 
 determining a second energy spectra for sub-pixel simultaneous detection events and determining its peak value V SPpeak2 ; and 
 calculating the sub-pixel charge sharing correction factor as (V SPpeak1 −V SPpeak2 )/V SPpeak2 . 
 
     
     
       7. The method of  claim 6 , wherein adjusting the energy measurements of sub-pixel simultaneous detection events by a charge sharing correction factor comprises multiplying measured energies of sub-pixel simultaneous detection events by a factor of one plus the sub-pixel charge sharing correction factor. 
     
     
       8. A method of calibrating a pixel radiation detector comprising an array of pixels each comprising an array of sub-pixel detectors to account for inter-sub-pixel charge sharing effects, comprising:
 exposing the imaging radiation detector to radiation from a source of gamma photons of a known energy or energy spectrum; 
 measuring gamma photon energies detected by the pixel radiation detector using electronics capable of registering simultaneous, coincident detection events occurring in two or more sub-pixel detectors within a pixel; 
 determining energies of gamma photons detected in sub-pixel detectors within a pixel for detection events occurring simultaneously in two or more sub-pixel detectors within a pixel which comprise sub-pixel simultaneous detection events; and 
 determining a sub-pixel charge sharing correction factor based upon the radiation source known gamma photon energy and determined energies of gamma photons detected in sub-pixel detectors within a pixel in sub-pixel simultaneous detection events to account for the inter-sub-pixel charge loss effects. 
 
     
     
       9. The method of  claim 8 , wherein determining a sub-pixel charge sharing correction factor based upon the radiation source known gamma photon energy and determined energies of gamma photons detected in adjoining pixels in sub-pixel simultaneous detection events accounts for inter-sub-pixel gap charge loss as a function of a difference between energies measured in sub-pixel detectors. 
     
     
       10. The method of  claim 8 , wherein determining a sub-pixel charge sharing correction factor based upon the radiation source known gamma photon energy and determined energies of gamma photons detected in adjoining pixels in sub-pixel simultaneous detection events comprises:
 determining a first energy spectra for detection events occurring in single pixels and determining its peak value V SPpeak1 ; 
 determining a second energy spectra for sub-pixel simultaneous detection events occurring and determining its peak value V SPpeak2 ; and 
 calculating the charge sharing correction factor as (V SPpeak1 −V SPpeak2 )/V SPpeak2 . 
 
     
     
       11. The method of  claim 8 , determining a sub-pixel charge sharing correction factor based upon the radiation source known gamma photon energy and determined energies of gamma photons detected in sub-pixel detectors in sub-pixel simultaneous detection events is performed for each pixel detector individually to determine a sub-pixel charge sharing correction factor for each pixel. 
     
     
       12. The method of  claim 11 , where in the method is performed as part of manufacturing the pixel radiation detector. 
     
     
       13. The method of  claim 12 , further comprising storing the sub-pixel charge sharing correction factors in memory associated with the pixel radiation detector. 
     
     
       14. An imaging radiation detector, comprising:
 an array of pixels each comprising an array of sub-pixel detectors; and 
 detector processing circuitry coupled to each sub-pixel detector, the detector processing circuitry capable of registering simultaneous, coincident detection events occurring in two or more sub-pixel detectors within any pixel and configured to:
 sum energy measurements of detection events occurring simultaneously in two or more sub-pixel detectors within a pixel which comprise sub-pixel simultaneous detection events to obtain a first energy measurement of multi-subpixel detection events; 
 adjust the first energy measurements of sub-pixel simultaneous detection events by a sub-pixel charge sharing correction factor to account for inter-sub-pixel charge loss effects; and 
 determine a corrected gamma photon energy spectrum by adding the adjusted energy measurements of sub-pixel simultaneous detection events to gamma photon energy measurements of detection events occurring in single sub-pixel detectors. 
 
 
     
     
       15. An imaging radiation detector, comprising:
 an array of pixels each comprising an array of sub-pixel detectors; 
 means for summing energy measurements of detection events occurring simultaneously in two or more sub-pixel detectors within a pixel which comprise sub-pixel simultaneous detection events to obtain a first energy measurement of multi-subpixel detection events; 
 means for adjusting the first energy measurements of sub-pixel simultaneous detection events by a sub-pixel charge sharing correction factor to account for inter-sub-pixel charge loss effects; and 
 means for determining a corrected gamma photon energy spectrum by adding the adjusted energy measurements of sub-pixel simultaneous detection events to gamma photon energy measurements of detection events occurring in single sub-pixel detectors.